FIELD TESTING AND EVALUATION OF DUST DEPOSITION AND ...

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four heights. The root mean sum of squares (RMS) was then computed from the relative difference between the calculated velocities and the measured velocities. The sum of the RMS over all 110 intervals was used as a weighting function. The final estimate for z 0 was obtained by minimizing the weighting function. Note that this method is superior to performing a regression for each 15-minute interval, since it provides a single value for z 0 that is applicable to all intervals. 20 15 DustTrak Reading (mg/m3) 10 5 Vehicle passes by DT_1 0 Baseline DT_1 DT_2 DT_3 -5 18:02:10 18:02:27 18:02:44 18:03:01 18:03:19 18:03:36 18:03:53 18:04:11 Time Figure 5-2. Example of time series of DustTrak PM 10 concentrations after the passage of a vehicle on the unpaved road at Ft. Bliss. The arrows in the figure illustrate the start and stop times estimated for a baseline reading and the dust plume passing through the downwind towers DT_1, DT_2, and DT_3. The final value of 0.005 m obtained for z 0 lies between those expected for “level desert” (0.001 m) and “lawn” (0.01 m) (Seinfeld and Pandis, 1999). Figure 5-3 shows the distribution of u * values over the 111 intervals. Ninety-five percent of the values of u * fell between 10 and 50 cm/s, with values between 30 and 40 cm/s occurring most frequently (35%). Examples of how the wind speed fitted to a logarithmic vertical profile compares with the measured wind speed are given in Figure 5-4 for conditions corresponding to the lightest, most frequent, and heaviest winds observed over the 110 15-minute intervals. In general, the logarithmic fit is reasonable for all cases, though the wind speed at 12.2 meters is overestimated in the case of light winds. This may be caused by small differences in the resistance to motion among the four cup anemometers used. The fact that in Figure 5-4a the measured wind speed at 12.2 meters is slightly less than that at 5.7 meters supports this hypothesis. 5.1.1.1 Emission Tests Road dust emissions were created by having a test vehicle travel back and forth along the roadway for a number of passes. This ranged from a minimum of 20 to a maximum of 102. The mean number of vehicle passes was 49. The test vehicles traveled at set speeds of 16, 24, 32, 40, 48, 56, 64, 72, and 81 km/hr. Not all vehicles attained the highest speeds for safety considerations. After two passes (one heading south and one returning north) at the same speed, the vehicle speed was increased incrementally to the 5-4
100% 90% 80% Relative Frequency (probability) Cumulative % Relative Frequency 70% 60% 50% 40% 30% 20% 10% 0% 0 -10 10 - 20 20 - 30 30 - 40 40 - 50 50 - 60 > 60 u* (cm/s) Figure 5-3. Frequency distribution and cumulative distribution of u * for the 110 15-minute intervals corresponding to periods when testing was ongoing at Ft. Bliss. The u * values are based on a roughness height, z 0 equal to 0.005 m. u*= 10 cm/s u*= 32 cm/s u*= 54 cm/s 14 u(z) measured u(z) fitted 14 u(z) measured u(z) fitted 14 u(z) measured u(z) fitted 12 12 12 Height (z) in meters 10 8 6 4 Height (z) in meters 10 8 6 4 Height (z) in meters 10 8 6 4 2 2 2 0 12 16 20 24 u(z)/u * 0 12 16 20 24 u(z)/u* a. b. c. 0 12 16 20 24 u(z)/u* Figure 5-4. Examples of comparison between measured wind speed and wind speed calculated from curve fitting of Equation 2-9. a. light winds (u * =10 cm/s), b. medium winds (u * = 32 cm/s), c. high winds (u * = 54 cm/s). The roughness height, z 0 is equal to 0.005 m in all cases. 5-5
Page 1:
FIELD TESTING AND EVALUATION OF DUS
Page 5 and 6:
EXECUTIVE SUMMARY The Western State
Page 7 and 8:
models. Countess (2001) summarized
Page 9 and 10:
TABLE OF CONTENTS 1. INTRODUCTION 1
Page 11 and 12:
TABLE OF FIGURES Figure 2-1. Develo
Page 13 and 14:
Figure 4-6. The fraction of particl
Page 15 and 16:
Figure 5-16. Comparison of fraction
Page 17 and 18:
LIST OF TABLES Table 2-1. Parameter
Page 19 and 20:
1. INTRODUCTION 1.1 Background The
Page 21 and 22:
2.BACKGROUND Fugitive dust is emitt
Page 23 and 24:
Planetary Boundary Layer (PBL) F =
Page 25 and 26:
C D u* = ur The overall drag c
Page 27 and 28: St a vg u g = cA L * Equation 2
Page 29 and 30: Table 2-1. Parameters used in the S
Page 31 and 32: 1E+01 1E+00 z0 = 4.4 cm z0 = 6.4 cm
Page 33 and 34: pathway for deposition for particle
Page 35 and 36: An alternative method for modeling
Page 37 and 38: 3. MEASUREMENT OF DEPOSTION VELOCIT
Page 39 and 40: Department at the University of Uta
Page 41 and 42: In the laboratory, the deposited ma
Page 43 and 44: Table 3-2. Log of all flat substrat
Page 45 and 46: 16 Normalized Deposition Velocity 1
Page 47 and 48: 1.E+05 Deposition Velocity - cm/s 1
Page 49 and 50: are deposition from a horizontally
Page 51 and 52: single element that is intended to
Page 53 and 54: 4. MODELS USED TO STUDY PARTICLE RE
Page 55 and 56: κu ( ) * z 8 fz K zz = exp −
Page 57 and 58: C = −6 ( 1× 10 ) QV 2π u s σ
Page 59 and 60: oad. M is the mass of particles in
Page 61 and 62: By making the approximation that dm
Page 63 and 64: diameters less than 10 microns. Dis
Page 65 and 66: of such a height is somewhat arbitr
Page 67 and 68: 1 0.9 0.8 1 0.9 0.8 Fraction remain
Page 69 and 70: Fraction of Particles Remaining in
Page 71 and 72: gravitational settling. Stable cond
Page 73 and 74: though it is expected to improve at
Page 75 and 76: 5. DETERMINATION OF PARTICLE REMOVA
Page 77: PM 10 measured by the DustTrak must
Page 81 and 82: average wind speed measured at 12 m
Page 83 and 84: where the subscript i indicates tha
Page 85 and 86: k C int = peakend k C peeakstart d
Page 87 and 88: Height z (m) 14 12 10 8 6 T1_data T
Page 89 and 90: Horizontal fluxes of PM 10 measured
Page 92 and 93: Table 5-2 enumerates the speed-depe
Page 94 and 95: 6 Ratio of AP-42 Emission Factor to
Page 96 and 97: to the ground) giving an approximat
Page 98 and 99: models analyzed in this study is su
Page 100 and 101: Table 6-1. Screen analysis of test
Page 102 and 103: value which was used up to the midp
Page 104 and 105: measured at 3,1. Downwind the dust
Page 106 and 107: trips, the average readings for the
Page 108 and 109: Fraction of particles of stated siz
Page 110 and 111: the ground, where particles have a
Page 112 and 113: particles through the top of the bo
Page 114 and 115: deposition. Much of the decrease in
Page 116 and 117: 7-8
Page 118 and 119: Gifford, F.A. (1961). Use of Routin
Page 120: Venkatram, A. (1993). The Parametri
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